Many proposals have been made and known for a solid catalyst component containing magnesium, titanium, an electron donor compound and halogen as essential components and a process for the polymerization or the co-polymerization of olefins in the presence of a catalyst for polymerization of olefins comprising said solid catalyst component, an organic aluminum compound and an organic silicon compound. For example, JP-A-57-63310 and JP-A-57-63311 (The term "JP-A as used herein means an "unexamined published Japanese patent application") propose a process for polymerizing an olefin having 3 or more carbon atoms using a catalyst system comprising a solid catalyst component containing a magnesium compound, a titanium compound and an electron donor compound, an organic aluminum compound and an organic silicon compound having Si--O--C bond. However, these processes are not always satisfactory for obtaining highly stereoregular polymers in a high yield, and further improvement has been demanded.
On the other hand, JP-A-63-3010 discloses a catalyst system for the polymerization of olefins and a process for polymerizing olefins using the same, the catalyst system comprising a solid catalyst component prepared by bringing a dialkoxymagnesium, a diester of an aromatic dicarboxylic acid, an aromatic hydrocarbon and a titanium halide into contact and subjecting the resulting product in a powdered state to a heat treatment, an organic aluminum compound and an organic silicon compound. JA-A-1-315406 discloses a catalyst system for polymerizing olefins comprising a solid catalyst component prepared by bringing titanium tetrachloride with a suspension formed by diethoxymagnesium with an alkylbenzene, adding phthalic dichloride thereto to react to obtain a solid product, and further contacting the resulting solid product with titanium tetrachloride in the presence of an alkylbenzene, an organic aluminum compound and an organic silicon compound, and a process for polymerizing olefins in the presence of said catalyst system. The foregoing known techniques focus on the development of a catalyst component having a high activity enough to allow the omission of a so-called deashing step, i.e., a step of removing catalyst residues such as chlorine and titanium remaining in the polymer produced as well as on the enhancement of the yield of stereoregular polymer or an improvement in durability of the catalyst activity for polymerization, and achieved excellent results to these purposes.
The polymer obtained by using the foregoing catalyst is utilized in various uses, e.g., a container or a film other than a molded product of automobile or household appliances. These products are molded in various kind of molding machines by melting a polymer powder produced in polymerization. Especially, when a large molded product is produced by injection molding, there is a case that a high flowability (melt flow) of a melting polymer is needed. For such case, many researches are made in order to improve the melt flow of a polymer.
The melt flow depends on the molecular weight of a polymer greatly. In this field, an addition of hydrogen as a control agent for molecular weight of a polymer is conducted generally at the polymerization of olefins. In this case, when a polymer having a low molecular weight is produced, i.e., a polymer having high melting flow is produced, much hydrogen is added at the polymerization. However, there is a limitation for the amount of hydrogen that can be added because the capacity to resist pressure from the standpoint of safety. In order to add much hydrogen, it can not avoid reducing the partial pressure of monomer to be polymerized. In that case, the productivity deteriorates. Further, since much hydrogen is used, there is a problem on the cost. Therefore, it is desired to develop a catalyst that can produce a polymer having a high melt flow at fewer hydrogen, i.e., a catalyst that shows a high hydrogen response and can produce a high stereoregular polymer in a high yield. However, the foregoing known techniques are not enough to solve the problems.
As a result of extensive investigations to solve the foregoing problems remaining in the prior art techniques, the present inventors have found that a catalyst for polymerization of olefins having a high hydrogen response while maintaining a high activity and a high stereoregularity can be obtained by using a solid catalyst component containing magnesium, titanium, an electron donor compound and a halogen atom as essential components and satisfying a specific condition of a parameter obtained by Raman spectroscopic method, and thus completed the present invention.
The objective of the present invention is to solve the foregoing problems remaining in the prior art techniques and to provide a solid catalyst component and a catalyst for polymerization of olefins having a higher hydrogen response and a high activity, which can be obtained a high stereoregular polymer in a high yield.